From the Gateway Menu, choose the option “Boot Gateway Mode” to be taken to the update screen where you can get the latest firmware on your Gateway 3DS Red cart. Follow the steps to begin updating your cart. This process takes about a minute, but you may want to have your power cord plugged in, just to be safe.

After it’s updated turn the console off.

Place your game ROMs onto your Gateway’s MicroSD card with your computer, they can be either in .3ds or .3dz format.

Insert the microSD into your Gateway and the Gateway into your console.

Boot into the Homebrew Launcher and start the Gateway app.

From the Gateway Menu, select “Boot Gateway Mode”.

From the 3DS Home Menu, press the Select button and a ROM selector will appear on your top screen: